Perform initial refactoring work

Things that were once singletons are no longer singletons, but are
instead stored in the "Application" singleton

Some singletons still remain, and some renaming/renamespacing is left

src/application.hpp

@@ -7,16 +7,59 @@
 
 namespace chatterino {
 
+namespace singletons {
+
+class ThemeManager;
+class WindowManager;
+class LoggingManager;
+class PathManager;
+class CommandManager;
+class AccountManager;
+class EmoteManager;
+class PubSubManager;
+class NativeMessagingManager;
+class SettingManager;
+
+}  // namespace singletons
+
 class Application
 {
+    Application(int _argc, char **_argv);
+
 public:
-    Application();
-    ~Application();
+    static void instantiate(int argc, char **argv);
+
+    ~Application() = delete;
+
+    void construct();
+    void initialize();
+    void load();
 
     int run(QApplication &qtApp);
 
-private:
+    singletons::PathManager *paths = nullptr;
+    singletons::ThemeManager *themes = nullptr;
+    singletons::WindowManager *windows = nullptr;
+    singletons::LoggingManager *logging = nullptr;
+    singletons::CommandManager *commands = nullptr;
+    singletons::AccountManager *accounts = nullptr;
+    singletons::EmoteManager *emotes = nullptr;
+    singletons::PubSubManager *pubsub = nullptr;
+    singletons::NativeMessagingManager *nativeMessaging = nullptr;
+    singletons::SettingManager *settings = nullptr;
+
     void save();
+
+    // Special application mode that only initializes the native messaging host
+    static void runNativeMessagingHost();
+
+private:
+    int argc;
+    char **argv;
 };
 
+Application *getApp();
+
+bool appInitialized();
+
 }  // namespace chatterino